Method and apparatus for measuring the diameter of a rod-shaped article

ABSTRACT

An apparatus and a method for measuring the diameter of at least one rod-shaped article. A beam splitter is arranged to split a beam coming from the radiation source into several component beams and to conduct the beams from different directions onto the rod-shaped article. A detection device includes a plurality of detectors each arranged to generate a signal indicating a shading of a respective one of the component beams caused by the rod-shaped article. The rod-shaped article is positioned in or guided through the beam paths between the radiation source and the detection device and the diameter of the rod-shaped article is determined from the signals generated in the detection device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of German Application No. 10 2004049 879.2-54, filed on Oct. 13, 2004, the subject matter of which isincorporated herein by reference. The content of each U.S. and foreignpatent and patent application mentioned below is additionallyincorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for measuring the diameter of atleast one rod-shaped article, in particular of the tobacco industry,with the aid of at least one preferably optical measuring arrangement,comprising a radiation source for generating a beam designed toirradiate the rod-shaped article, and a detection device for generatingsignals to indicate the shading of the beam caused by the rod-shapedarticle, wherein the rod-shaped article can be positioned in or can beguided through the beam path between the radiation source and thedetection device and wherein the diameter of the rod-shaped article canbe determined from the signals generated by the detection device. Theinvention furthermore relates to a method for measuring the diameter ofat least one rod-shaped article, in particular of the tobacco industry,the method comprising the steps of irradiating the rod-shaped articlewith a preferably optical beam, generating the signals indicating theshading of the beam caused by the rod-shaped article, and determiningthe diameter of the rod-shaped article from these signals.

The term “rod-shaped article of the tobacco industry” in particular isunderstood to refer to cigarettes with or without filters, filter rods,cigarillos, cigars, and other types of smoking articles, regardless ofthe production stage these articles. The term “rod-shaped article”furthermore also comprises a continuous rod, which is present during aspecific production stage either as a complete rod section or a dividedrod section, e.g. for producing the aforementioned smoking article.

The diameter represents an essential quality feature that must bemonitored during the production of cigarettes and filters. For this, therod-shaped articles are generally aligned in the direction of theirlongitudinal axis and are transported either continuously ordiscontinuously through a measuring arrangement.

The difficulty with obtaining precise measurements of the diameter isthat the rod-shaped articles are frequently “out of round,” meaningtheir cross sections perpendicular to the longitudinal axes deviate moreor less from a circular shape.

European Patent EP 0 909 537 A1 discloses a measuring arrangement inwhich the radiation source generates a parallel-focused, wide beam whichis reflected by 90° by a mirror onto a detection device. The rod-shapedarticle extends parallel to the mirror and at a right angle to the beampath and, in the process, is positioned such that a portion of the beamcoming from the radiation source travels directly to the rod-shapedarticle while another portion of the beam arrives on the rod-shapedarticle after being reflected by the mirror. Thus, the beam impinging onthe detection device comprises two side-by-side arranged areas ofshading which represent the diameter in the form of two cross-sectionalaxes arranged at a right angle to each other. To be sure, this knownmeasuring arrangement is also suitable for rod-shaped articles which donot require a rotation around their longitudinal axis or for which sucha rotation is not desirable during the operation and is thus inparticular suitable for continuous rods. However, measuring the diameterby only two cross-sectional axes is not precise enough in many cases.

German Patent Document DE 195 23 273 A1 furthermore describes a methodand an arrangement for measuring the diameter of a rod-shaped article,in particular a cigarette, of the tobacco industry, wherein therod-shaped article is rotated and subjected to radiation during thetransport through a stationary measuring arrangement. The dimensions ofthe shading caused by the rod-shaped article are detected accordingly,are converted to an electric measuring signal, and a signal for thediameter of the rod-shaped article is generated from several suchmeasuring signals. To be sure, the measuring accuracy can be increasedwith this known arrangement, but the known arrangement in particular isnot suitable for measuring the diameter of a continuous rod which doesnot rotate around its longitudinal axis.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and anapparatus of the aforementioned type which permits extremely accuratediameter measurements of rod-shaped articles, without having to subjectthe measuring arrangement and the rod-shaped articles to a rotatingmovement and which is therefore particularly suitable for diametermeasurements on continuous rods.

The above and other objects are accomplished according to a first aspectof the invention wherein there is provided an apparatus for measuringthe diameter of a rod-shaped article, comprising: a radiation source forgenerating a beam; a beam splitter arranged to split the beam comingfrom the radiation source into several component beams and to conductthe beams from different directions onto the rod-shaped article; and adetection device including a plurality of detectors each arranged togenerate a signal indicating a shading of a respective one of thecomponent beams caused by the rod-shaped article, wherein the rod-shapedarticle is positioned in or guided through the beam paths between theradiation source and the detection device and the diameter of therod-shaped article is determined from the signals generated in thedetection device.

According to a second aspect of the invention, there is provided amethod for measuring the diameter of a rod-shaped article, comprising:generating a beam of radiation; splitting the beam into severalcomponent beams that are conducted from different directions onto therod-shaped article; generating separate signals each of which indicate ashading of a respective one of the component beams caused by therod-shaped article; and determining the diameter of the rod-shapedarticle from the signals.

The invention accordingly consists of using a corresponding number ofcomponent beams, obtained by splitting the (main) beam generated by theradiation source, for a plurality of diameter measurements of therod-shaped article. Each measurement occurs from a different perspectivesince the component beams according to the invention are guided fromdifferent directions onto the rod-shaped article. The higher the numberof component beams used and the number of resulting measurements, thehigher the precision for determining the cross-sectional shape of therod-shaped article.

An advantages achieved with the invention is that the diameter of therod-shaped article can be determined with extreme accuracy, inparticular for rod-shaped articles that are not round while. Anotheradvantage is that a rotational movement of the measuring arrangement ora rotation of the rod-shaped article around its longitudinal axis is notrequired and the measurement according to the invention therefore doesnot require rotating components. The invention is therefore especiallysuitable for use in cases where a rotational movement in particular isnot required or even desired for the processing, and thus the inventionis suitable, in particular, for continuous rods.

As a result of the latter, the rod-shaped article can remain immovableduring the measurement. Alternatively, it is also conceivable andespecially advantageous for the operation if the rod-shaped article ismoved continuously or discontinuously in a longitudinal axial directionthrough the measuring arrangement, wherein during one stage of theproduction of the rod-shaped articles, a continuous rod can be present,which can be transported in the longitudinal axial direction through themeasuring arrangement, either as a single continuous rod section or asalready divided continuous rod sections.

Owing to the fact that the invention permits a nearly infinite number ofdiameter measurements at one and the same location of a rod-shapedarticle, it is also possible to detect the cross-sectional shape and the‘out of roundness,’ as well as the minimum and maximum diameter of therod-shaped article. The latter is particularly important for determiningwhether the diameter is still within permissible limits. The inventionfurthermore can be used particularly advantageously for measuringcigarettes and filter plugs having an elliptical cross section, so thatmatching filter plugs and cigarette rods can be detected.

The beam splitter advantageously guides the component beams onto therod-shaped article so that each component beam is shaded only partiallyby the rod-shaped article. The detection device thus detectsside-by-side arranged light-dark transitions of the component beams,arriving from different directions on the rod-shaped article, from whichthe diameter and/or thickness of the rod-shaped article can bedetermined, respectively in the directions perpendicular to thecomponent beams.

The diameter of the rod-shaped article is generally determined from thesignals coming from the detection device in an evaluation unit,installed downstream of the detection device. An average-value former inthe evaluation unit is preferably used to form an average value of thesignals coming from the detecting means.

According to one exemplary embodiment, the beam splitter is providedwith mirrors which deflect at least some of the component beams of themain beam in different directions and then onto the rod-shaped article.As an alternative or in addition, at least one prism can be providedwith at least one mirror surface which correspondingly deflects at leastsome of the component beams. The component beams are thus separated outof the main beam with the aid of the mirrors and/or the mirrorsurface(s).

It a further exemplary embodiment, there is provided abeam-recombination device, which recombines the component beams afterthey pass the rod-shaped article, so that they again form a single beamin which the component beams are essentially arranged parallel to eachother. The detectors in this case are substantially arrangedside-by-side in a row. A particularly simple embodiment of the detectiondevice is possible with this design since it is structurally very easyto combine the side-by-side arranged detectors. The beam-recombinationdevice is preferably also provided with mirrors and/or at least oneprism, comprising at least one mirror surface, such that it isparticularly easy to redirect the component beams to the same direction.

A device for the substantially parallel alignment of the beam comingfrom the radiation source may be provided between the radiation sourceand the beam splitter. A device of this type is particularly useful ifthe radiation source generates a diverging beam, as is generally thecase. Using such a device can also simplify the splitting of the beaminto component beams since only the individual parallel sections of themain beam must be separated out to form component beams, owing to theparallel alignment. A device of this type is preferably provided with acollimator lens. A cylindrical lens can furthermore be installeddownstream of the device and can be used advantageously for generatingcomponent beams.

A laser, in particular a laser diode, can advantageously be used as aradiation source and/or the detecting means can be charge-coupled deviceelements.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the invention will be furtherunderstood from the following detailed description of the preferredembodiments with reference to the accompanying drawings.

FIG. 1 shows a perspective, schematic view of a continuous cigarette rodmachine, showing the essential structural components.

FIG. 2 shows a schematic view of a first exemplary embodiment accordingto the invention of an optical measuring arrangement with its essentialcomponents, used in the continuous cigarette rod machine shown in FIG.1, which is positioned at a right angle to the longitudinal axis andmovement direction of the continuous cigarette rod.

FIG. 3 shows a schematic view of a second exemplary embodiment accordingto the invention of an optical measuring arrangement with its essentialcomponents, used in the continuous cigarette rod machine shown in FIG.1, which is positioned at a right angle to the longitudinal axis andmovement direction of the continuous cigarette rod.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic, perspective view of a continuous cigarette rodmachine of the type “PROTOS,” manufactured by the assignee of thepresent invention, in which the main components are visible. The designand function of this continuous cigarette rod machine are brieflydescribed in the following.

An airlock 1 supplies a pre-distributing device 2 with batches oftobacco. In a controlled operation, a withdrawing roller 3 of thepre-distributing device 2 is used to supplement the tobacco in a storagecontainer 4 from which a vertical conveyor 5 removes the tobacco. In acontrolled operation, the vertical conveyor then feeds this tobacco toan accumulation chute 6. A pin roller 7 removes a uniform stream oftobacco from this accumulation chute 6 and a beater roller 8 then beatsthe tobacco out of the pins of the pin roller 7 and tosses the tobaccowith a constant speed onto a circulating distributing web 9.

A fibrous tobacco fleece, formed in this way on the distributing web 9,is subsequently tossed into a sifting device 11 which essentiallyconsists of an air curtain through which larger and/or heavier tobaccoparticles pass while all other tobacco particles are directed by the airinto a funnel 14 that is formed by a pin roller 12 and a wall 13. Fromthe pin roller 12, the tobacco is tossed into a tobacco channel 16 andonto a continuous rod conveyor 17 against which the tobacco is held byair suctioned into a low-pressure chamber 18, to form a continuoustobacco rod.

A straightening device 19 removes excess tobacco from the continuoustobacco rod which is then placed onto a synchronously conveyedcigarette-paper strip 21. The cigarette-paper strip 21 is pulled from abobbin 22, is guided through a printing device 23, and is then placedonto a driven format belt 24. The format belt 24 transports thecontinuous tobacco rod and the cigarette-paper strip 21 through a formatmachine 26 in which the cigarette-paper strip 21 is folded around thecontinuous tobacco rod, so that one edge still sticks up. This edge iscoated with glue by means of a glue applicator, not shown herein,whereupon the glue seam is closed and dried by means of a tandem seamsmoothing iron 27.

A continuous cigarette rod 28, formed in this way, passes through ameasuring and control unit 29 and is cut into double-length cigarettes32 with a knife apparatus 31. The double-length cigarettes 32 are thentransferred onto a takeover drum 36 of a filter-tipping machine 37 bymeans of a transfer device 34 with controlled arms 33. On the cuttingdrum 38 of the filter-tipping machine, they are cut with a circularknife into individual cigarettes.

Conveying belts 39, 41 convey excess tobacco into a container 42,arranged below the storage container 4, from which the returned tobaccois removed again with the aid of the vertical conveyor 5.

The measuring and control unit 29 of the continuous cigarette rodmachine according to FIG. 1 is provided with an optical measuringarrangement, of which a first exemplary embodiment 50 is shown in FIG. 2and a second exemplary embodiment 50 a is shown in FIG. 3.

The optical measuring arrangement 50 according to FIG. 2 comprises aradiation source 52, which is preferably provided with at least onelaser diode or consists of such a laser diode. The radiation source 52for the exemplary embodiment shown in FIG. 2 is designed to generate adiverging beam 54 a. The diverging beam 54 a is converted with the aidof a downstream-arranged collimator lens 56 to a parallel beam 54 b,which then passes through a cylindrical lens 58.

Behind the cylindrical lens 58, the parallel beam 54 b, which can becalled a main beam in the same way as the beam 54 a, is split intocomponent beams 601 to 608 that impinge from different directions ontothe continuous cigarette rod 28, such that each component beam is shadedonly partially by the continuous cigarette rod 28. In the process, thecontinuous cigarette rod 28 is guided through the optical measuringarrangement 50 so that the component beams 601 to 608 extendapproximately at a right angle to the longitudinal axis, which extendsat a right angle to the drawing plane for FIG. 2, thus causing thecomponent beams to extend at a right angle to the movement direction ofthe continuous cigarette rod 28.

FIG. 2 furthermore shows that the component beams 601 to 608 initiallyform side-by-side arranged parallel beam sections of the main beam 54 b,directly behind the cylindrical lens 58. The component beams 601 to 608of the exemplary embodiment are subsequently reflected on mirrors,wherein some of the component beams are deflected only after theyimpinge on the continuous cigarette rod 28 and other component beams aredeflected before they impinge on the continuous cigarette rod 28.

The first component beam 601, the ‘upper’ component beam in FIG. 2, isinitially deflected by 45° on a mirror 621 and onto a mirror 641, whereit is deflected by 90° onto the continuous cigarette rod 28. In the sameway, the adjacent second component beam 602 is initially deflected by45° on a mirror 622 and subsequently by 90° on a mirror 642 in thedirection of the continuous cigarette rod 28. While the mirrors 621 and622 are arranged side-by-side, such that the first and second componentbeams 601 and 602 continue to extend parallel following the reflection,the two mirrors 641 and 642 are spaced apart such that the firstcomponent beam 601 grazes one side of the continuous cigarette rod 28and the second component beam 602 grazes the opposite side of thecontinuous cigarette rod 28. Accordingly, the spacing between the twomirrors 641 and 642 is determined by the thickness of the continuouscigarette rod 28. However, the orientation of the mirrors 641 and 642relative to each other is identical, so that these mirrors 641 and 642are aligned parallel.

The third component beam 603 is reflected by 90° on a mirror 623 andsubsequently impinges directly onto the continuous cigarette rod 28. Thesame happens with the fifth component beams 605, which is deflected on amirror 625. As a result, the third component beam 603 and the fifthcomponent beam 605 are aligned parallel when they pass the continuouscigarette rod 28, with the third component beams 603 grazing one side ofthe continuous cigarette rod 28 and the fifth component beam 605 grazingthe opposite side of the continuous cigarette rod 28. The two mirrors623 and 625 are accordingly spaced apart, but have the same orientation.Thus, upon their arrival on the continuous cigarette rod 28, the thirdcomponent beam 603 and the fifth component beam 605 extend at an angleof 45° relative to the first component beam 601 and the second componentbeam 602.

The fourth component beam 604 and the sixth component beam 606 also forma pair and pass the continuous cigarette rod 28 at a right angle,relative to the first component beam 601 and the second component beam602. For this, the fourth component beam 604 is reflected on a mirror624 and the sixth component beam 606 is reflected on a mirror 626 by 45°in the direction of the continuous cigarette rod 28, wherein the twomirrors 624 and 626 extend parallel to each other, but are spaced apartsuch that the fourth component beam 604 grazes the continuous cigaretterod 28 on one side and the sixth component beam 606 grazes thecontinuous cigarette rod 28 on the opposite side.

In contrast to the component beams 601 to 606, the seventh componentbeam 607 and the eighth component beam 608 are focused by means of thecylindrical lens 58 directly onto the continuous cigarette rod 28 beforebeing reflected by the mirrors 627 and/or 628 which are installed behindcontinuous cigarette rod 28. The seventh component beam 607 and theeighth component beam 608 are spaced apart for this, such that theseventh component beam 607 grazes the continuous cigarette rod 28 on oneside and the eighth component beam 608 grazes the continuous cigaretterod 28 on the opposite side. The spaced-apart seventh and eighthcomponent beams 607 and 608, which are not subjected to a change indirection before they pass by the continuous cigarette rod 28, thereforeextend at an angle of 135° to the first and second component beams 601and 602.

For the exemplary embodiment shown herein, the parallel component beams601 to 608 have the same constant cross section over their course.However, configurations with changing cross sections for the componentbeams are also conceivable as well, for example following a reflectionon a mirror. It is furthermore conceivable, in principle, to formconverging or diverging beams if necessary.

Owing to the previously described course of the component beams 601 to608, a partial shading of the continuous cigarette rod 28 occurs over anangular region of approximately 90° for the exemplary embodiment,wherein the shaded angular regions overlap, as shown in FIG. 2.

Of course, the width and the spacing between component beams can beadjusted through a corresponding configuration of the reflectingmirrors, so as to shade an angular region of less than 90°. However, theangular shading region selected for the exemplary embodiment, which useseight component beams for irradiating the continuous cigarette rod 28,should not be less than 45° because undesirable gaps in the form ofnon-shaded regions can otherwise develop. The angular region to beshaded should furthermore not exceed 180° to prevent an undesirableoverlapping of two parallel component beams belonging to the same pair,thus making it difficult or even impossible to assign these clearly.

FIG. 2 shows that the component beams directly behind the cylindricallens 58 are defined so that the first to the sixth component beams 601to 606 are positioned directly adjacent to each other while the seventhcomponent beam 607 is at a distance from the sixth component beam 606 aswell as at a distance from the eight component beam 608, wherein FIG. 2shows that the distance respectively corresponds to the width of acomponent beam. The gap between the sixth component beam 606 and theseventh component beam 607, as well as the gap between the seventhcomponent beam 607 and the eighth component beam 608 furthermorecontains beam sections belonging to the main beam 54 a which, in thesame way as the component beams 601 to 608, represent component beams.However, these component beams are not used further because the beamsection between the sixth component beam 606 and the seventh componentbeam 607 is reflected back by the mirror 641, directly onto thecylindrical lens 58, while the beams section between the seventhcomponent beam 607 and the eight component beam 608 is completely shadedby the continuous cigarette rod 28. Accordingly, the exemplaryembodiment does not make use of the complete width of the main beam 54 bfor forming the relevant component beams 601 to 608. It should be notedhere that other configurations are conceivable, of course, which use ahigher or lower number of component beams for the partial shading of thecontinuous cigarette rod 28. For example, it is also possible to use allbeam sections of the main beam 54 b to form the relevant componentbeams.

FIG. 2 furthermore shows that the individual mirrors are configured suchthat their effective cross section for reflection does not exceed thecross section of the partial beam they reflect, so as to preventinterference between the respectively adjacent component beam. As aresult, the mirrors with the smaller reflection angles (e.g. the mirrors621, 622, 624, 626) have a greater length than the mirrors with thehigher reflection angles (e.g. 623, 625, 641, 642).

In place of the discrete mirrors shown in FIG. 2, it is furthermorepossible to use an optical element having reflective surface areasincorporated therein. Of course, it is also conceivable to use prisms orthe like in place of mirrors.

FIG. 2 and the preceding description clearly show that the mirrors 621,622, 623, 624, 625 and 626 also function as beam splitters. The same istrue for the mirror 627 on which the seventh component beam 607 isreflected by an angle of 90° (downward according to FIG. 2) after it haspassed the continuous cigarette rod 28, and the mirror 628 on which theeighth component beam 608 is also reflected by 90° after passing thecontinuous cigarette rod 28 (downward according to FIG. 2). The mirrors621 to 628 consequently form a beam splitter for the embodiment shownherein.

FIG. 2 furthermore shows that the component beams 601 to 608 of theexemplary embodiment are recombined later on to form a single beam byusing additional mirrors and are then conducted to the detector row 66.As a result of the above-described arrangement of the mirrors 641 and642 and after passing the continuous rod 28, the first component beam601 and the spaced apart, parallel second component beam 602 areconducted at a right angle directly onto the detector row 66. For thethird component beam 603 and the parallel, spaced apart fifth componentbeam 605, the mirrors 643 and 645 are provided between the continuouscigarette rod 28 and the detector row 66, on which these component beamsare reflected by about 45° before impinging at a right angle on thedetector row 66. Since the fourth component beam 604 and the parallel,spaced apart sixth component beam 606 extend approximately parallel tothe detector row 66 while passing the continuous cigarette rod 28, theadditional mirrors 644 and 646 are provided for deflecting these partialbeams by 90° in the direction of the detector row 66, wherein theembodiment shown herein respectively requires two additional mirrors627, 647 and 628, 648 for redirecting the seventh component beam 607 andthe eight component beam 608, which are arranged in the beam path afterthe continuous cigarette rod 28. Initially, the seventh and/or theeighth component beam 607 and/or 608 are reflected by 90° on the mirror627 and/or 628 (downward according to FIG. 2), before they are reflectedagain by 45° on the mirror 647 and/or 648 in the direction of thedetector row 66.

The mirrors 641 to 648 accordingly function as a beam-recombinationdevice for a parallel, side-by-side alignment of the component beams 601to 608, such that they form a single beam which impinges perpendicularon the detector row 66. It is apparent from FIG. 2 that the sequence ofthe individual component beams 601 to 608 is different when they impingeon the detector row 66 than when they exit the cylindrical lens 58.However, this fact does not play a role in the determination of thediameter. Of course, configurations with a different sequence for thecomponent beams are conceivable as well.

The component beams 601 to 608 for the embodiment shown herein aredeflected by 135° from the start to the end of their beam path beforeimpinging on the detector row 66. Of course, a different orientation forthe detector row 66 is also conceivable.

With respect to possible alternative configurations for the mirrors 641to 648, the same applies as previously stated for the mirrors 621 to628.

FIG. 3 shows a second preferred embodiment of a measuring arrangement 50a which differs from the measuring arrangement 50 shown in FIG. 2 inthat three separate prisms 72, 74 and 76 are provided in place ofdiscrete mirrors while the remaining components are the same as for theembodiment of the optical measuring arrangement 50 shown in FIG. 2.Thus, only the differences to the first embodiment according to FIG. 2are described in the following for the second embodiment of the opticalmeasuring arrangement 50 a according to FIG. 3.

The three separate prisms 72, 74, 76 are provided for splitting the mainbeam and aligning and recombining the component beams, wherein theprisms 72, 74, 76 are designed such that the component beams enter andexit the surface areas at a ninety degree angle to avoid diffractioneffects.

In contrast to the first embodiment according to FIG. 2, the parallelbeam 54 b of the second embodiment of the optical measuring arrangement50 a, shown in FIG. 3, is divided not into eight but into six componentbeams 601 to 606 behind the cylindrical lens 58.

The first component beam 601, the ‘top’ component beam in FIG. 3,initially enters the first prisms 72 through a first surface 721,aligned at a right angle, is then reflected by an opposite-arrangedsecond surface 722 of the first prism 72, arranged at an angle of 1200relative to the impinging component beam, in the direction of thecontinuous cigarette rod 28 and exits the prism 72 again through a thirdsurface 723, aligned at a right angle, such that it grazes one side ofthe continuous cigarette rod 28. Following this, the first componentbeam 601 enters a surface 761, aligned at a right angle, of the thirdprism 76 and exits again through an also right-angle aligned secondsurface 762 before it impinges on the detector row 66. In the same way,the neighboring component beam 602 is deflected by the first prism 72and is conducted through the third prism 76, wherein the secondcomponent beam 602 is spaced apart from the first component beam 601,such that the second component beam 602 grazes the continuous cigaretterod 28 on its opposite side.

The third component beam 603 enters the second prism 74 through itsright-angle aligned first surface 741, is reflected by an oppositearranged second surface 742 of the second prism 74, arranged at an angleof 1500 relative to the impinging component beam, and exits againthrough its third surface 743, positioned at a right angle to thecomponent beam, in the direction of the continuous cigarette rod 28,such that it grazes this rod on one side. Subsequently, the thirdcomponent beam 603 enters the third prism 76 through a third surface763, arranged at a right angle to this component beam, is reflected byan opposite-arranged fourth surface 764, positioned at a 1500 anglerelative to the impinging component beam, and exits the third prism 76through its second surface 762, which extends at a right angle to thiscomponent beam, such that it arrives at the detector row 66. The fourthcomponent beam 604 extends parallel to the third component beam 603 andthus follows the same course, but at a distance to the third componentbeam 603 and grazes the continuous cigarette rod 28 on the oppositeside.

The fifth component beam 605 passes through the second prism 74 withoutbeing reflected by entering the second prism 74 through its firstsurface 741, positioned at a right angle to the component beam, andexits the second prism 74 again through its fourth surface 744, which isalso aligned at a right angle to the component beam, such that it grazesthe continuous cigarette rod 28 on one side. Following this, the fifthcomponent beam 605 enters the first prism 72 through a fourth surface724, also positioned at a right angle, is then reflected by its slantedsecond surface 722 and exits again through its fifth surface 725,arranged at a right angle to the component beam, such that it impingeson the detector row 66. The same course is also followed by the sixthcomponent beam 606, which is conducted parallel to the fifth componentbeam 605, but at a distance thereto, and grazes the continuous cigaretterod 28 on the opposite side.

Similarly to the first embodiment shown in FIG. 2, the first and secondcomponent beams 601 and 602, the third and fourth component beams 603and 604, as well as the fifth and sixth component beams 605 and 606respectively form pairs which have the same alignment and take the samecourse.

FIG. 3 and the associated specification text clearly show that the threeprisms 72, 74, 76 take on the function of a beam splitter for splittingthe parallel beam 54 b into several—here six—component beams 601 to 606,which are then conducted from different directions onto the continuouscigarette rod 28. The prisms also function as a beam-recombinationdevice for recombining the individual component beams 601 to 606 in aparallel, side-by-side alignment to form a single beam that impingeswith a ninety degree angle on the detector row 66.

With respect to additional features and characteristics, reference ismade to the description of the first exemplary embodiment of the opticalmeasuring arrangement 50, shown in FIG. 2, to avoid repetition.

The detector row 66 comprises several side-by-side positioned detectingelements, wherein respectively one detecting element is assigned to onecomponent beam. However, it is also conceivable to have severaldetecting elements which respectively combine to form a group which isthen assigned to a defined component beam. It is advantageous if thedetecting elements are charge-coupled device elements.

The light-dark transitions of the component beams, which impinge fromdifferent directions on the continuous cigarette rod 28, are projectedside-by-side onto the detector row 66. These light-dark transitions areindicated schematically in FIG. 2, in a graph assigned to the detectorrow 66.

An evaluation unit 81 (shown in FIG. 2) which is positioned downstreamof the detector row 66 then computes the diameter of the continuouscigarette rod 28 from the light-dark transitions, respectively in thedirections extending perpendicular to the component beams. In this way,a precise measurement of the thickness of the continuous cigarette rod28 is obtained for various angular directions. The thickness of thecontinuous cigarette rod 28 can be determined over a 90° range sinceeight component beams 601 to 608 combined into four pairs are used forthe first embodiment shown in FIG. 2. Accordingly, the continuouscigarette rod 28 for the first embodiment according to FIG. 2 ismeasured in four different directions. FIG. 3 shows that only sixcomponent beams 601 to 606, combined into three pairs, are used for thesecond embodiment, wherein the thickness can be determined over a 120°range. For that reason, the continuous cigarette rod 28 is measured inonly 3 directions for the second embodiment according to FIG. 3.

If the number of component beams increases, a larger number ofmeasurements at a smaller angle division can be realized, thus making itpossible to increase the accuracy even further. In contrast, a reductionin the number of component beams leads to a lower number of measurementsover a larger angular distance.

Finally, the evaluation unit can also comprise an average-value former83 for forming the average value of the signals from the detector row66, so as to determine an average value for the diameter of thecontinuous cigarette rod 28.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

1. An apparatus for measuring the diameter of a rod-shaped article,comprising: a radiation source for generating a beam; a beam splitterarranged to split the beam coming from the radiation source into severalcomponent beams and to conduct the beams from different directions ontothe rod-shaped article; and a detection device including a plurality ofdetectors each arranged to generate a signal indicating a shading of arespective one of the component beams caused by the rod-shaped article,wherein the rod-shaped article is positioned in or guided through thebeam paths between the radiation source and the detection device and thediameter of the rod-shaped article is determined from the signalsgenerated in the detection device.
 2. The apparatus according to claim1, wherein the beam splitter conducts the component beams onto therod-shaped article so that each component beam is only partially shadedby the rod-shaped article.
 3. The apparatus according to claim 1,further including an evaluation unit coupled to the detection device todetermine the diameter of the rod-shaped article based on the signalsgenerated by the detection device.
 4. The apparatus according to claim3, wherein the evaluation unit includes an average-value former to forman average value from the signals generated by the detecting means. 5.The apparatus according to claim 1, wherein the beam splitter includesmirrors that deflect at least some of the component beams of the mainbeam so such that the component beams impinge from different directionson the rod-shaped article.
 6. The apparatus according to claim 1,wherein the beam splitter comprises at least one prism that deflects atleast some of the component beams of the main beam, such that thecomponent beams impinge from different directions on the rod-shapedarticle.
 7. The apparatus according to claim 1, further including a beamre-combination device arranged to recombine the component beams afterthey impinge on the rod-shaped article into a single beam in which thecomponent beams are substantially parallel to each other, wherein thedetectors are essentially aligned side-by-side in a row.
 8. Theapparatus according to claim 7, wherein the beam re-combination devicecomprises mirrors that redirect the component beams to the samedirection.
 9. The apparatus according to claim 7, wherein the beamre-combination device comprises at least one prism that redirects thecomponent beams to the same direction.
 10. The apparatus according toclaim 1, further including an alignment device positioned between theradiation source and the beam splitter to substantially parallel alignthe beam coming from the radiation source.
 11. The apparatus accordingto claim 10, wherein the alignment device comprises a collimating lens.12. The apparatus according to claim 10, further including a cylindricallens arranged downstream of the alignment device.
 13. The apparatusaccording to claim 1, wherein the radiation source comprises a laser.14. The apparatus according to claim 12, wherein the laser comprises alaser diode.
 15. The apparatus according to claim 1, wherein thedetectors comprise charge-coupled device elements.
 16. The apparatusaccording to claim 1, wherein the beam is an optical beam.
 17. A methodfor measuring the diameter of a rod-shaped article, comprising:generating a beam of radiation; splitting the beam into severalcomponent beams that are conducted from different directions onto therod-shaped article generating separate signals each of which indicate ashading of a respective one of the component beams caused by therod-shaped article; and determining the diameter of the rod-shapedarticle from the signals.
 18. The method according to claim 17, whereinthe splitting step includes conducting the component beams onto therod-shaped article so that each component beam is shaded only partiallyby the rod-shaped article.
 19. The method according to claim 17, furtherincluding recombining the component beams, after impinging on therod-shaped article, to form a single beam in which the component beamsare aligned substantially parallel to each other.
 20. The methodaccording to claim 17, and further including forming an average valuefrom the signals generated by the different component beams.
 21. Themethod according to claim 17, further including aligning the beam to beparallel before being split into component beams.
 22. The methodaccording to claim 17, wherein the step of generating a beam includesgenerating an optical beam.